Means for equalizing pressures in multiple cylinders of a stirling cycle engine

ABSTRACT

The working space of a Stirling cycle engine is connected to two chambers by means of valve arrangements tending to equalize pressures in the two chambers. A first of the chambers is at the maximum pressure attained in any of the cylinders and the second is at the maximum pressure for each single cylinder.

United States Patent 1191 Gothberg MEANS FOR EQUALIZING PRESSURES IN MULTIPLE CYLINDERS OF A STIRLING 2,746,241 /1956 Dros et a1. 60/24 1451 Apr. 9, 1974 3,559,398 2/1971 Meijer et a1. ..60/24 3,699,770 /1972 Bennethum ..60/24 Primary Examiner-Edgar W. Geoghegan Assistant Examiner-H. Burks, Sr. Attorney, Agent, or Firm-Laurence R. Brown, Esq.

[ 5 7] ABSTRACT The working space of a Stirling cycle engine is connected to two chambers by means of valve arrangements tending to equalize pressures in the two chambers. A first of the chambers is at the maximum pressure attained in any of the cylinders and the second is at the maximum pressure for each single cylinder.

1 6 Claims 2Drawing Figures s 29 -s 7 j 8 T- Q .LT- J T -1T 14 1s h' & l' 18/ g -l l" ZO /L' MEANS FOR EQUALIZING PRESSURES IN MULTIPLE CYLINDERS OF A STIRLING CYCLE ENGINE This invention relates to a multi-cylinder, doubleacting Stirling cycle engine, herein called an engine of the kind referred to.

In an engine of the kind referred to each cylinder contains a piston dividing from one another two working gas charges appertaining to two different working gas circuits in cycles which are synchronous but out of phase with each other. Thus in the event of gas leaking between the piston and the cylinder wall, it may occur that during the working cycles of one working gas charge the gas therein has a higher mean pressure than that in the gas during the working cycles in other working gas charges. A higher mean pressure will result in a higher effective output, and thus an uneven power output distribution among the cylinders of the engine and thus an uneven temperature distribution. For reasons of safety, the governing of the temperature must be based upon the engine cylinder having the highest temperature, and consequently an uneven temperature distribution will result in a decrease of the efficiency and of the total output of the engine.

Therefore, it is an object of the present invention to avoid the persistence of different mean pressures in the separate working gas charges of an engine of the kind referred to.

According to the present invention an engine of the kind referred to is characterised in that the low temperature compression working space of each cylinder is connected to two chambers, namely a first chamber and a second chamber, the first chamber containing working gas at a pressure corresponding to the maximum cycle pressure of the said low temperature working space whereas the second chamber contains working gas at a pressure corresponding to the maximum pressure reached during a working cycle in any one of the engine spaces, means being provided for comparing the pressures in the said two chambers and means being provided for passing gas from the said second chamber into the low temperature working space if the pressure in the said second chamber exceeds the pressure in the said first chamber.

The scope of the monopoly sought is defined in the claims hereinafter and how the invention can be put into the practice is described in more detail with reference to the accompanying drawing in which FIG. 1 schematically and in vertical section shows a four-cylinder, double acting Stirling cycle engine according to the invention by way of example, and

FIG. 2 represents a part of FIG. 1 to a larger scale.

The engine shown comprises four cylinders 1 4 each accommodating a reciprocating piston 5 8 provided with a piston rod 9 12 respectively.

Each piston 5 8 divides the cylinder 1 4 in which it is accommodated into working spaces of variable volumes an upper high temperature expansion space and a lower low temperature compression space. The upper space 13 of the cylinder 2 is connected with the lower space 14 of the cylinder 1. Similarly the upper spaces 15, 17 and 19 of the cylinders 3, 4 and l are connected with the lower spaces 16, 18 and 20 of the cylinders 2, 3 and 4 respectively. The connections are established by pipes containing units 21 24 each ineluding a regenerator and a cooler. The upper spaces 13, 15, 17 and 19 are heated by heating devices (not shown) and are thus kept at a high temperature level. The lower spaces 14, l6, 18, 20 are kept at a low temperature level due to the coolers in the units 21 24. The volume variations of each of the upper spaces at the high temperature level are 90 in advance of the volume variations of the lower space with which it is connected. The engine shown will contain four separate working gas charges, the separation of these charges from each other being effected by the pistons. The working gas is hydrogen or helium at a high pressure, which during operation may vary between e.g. 250 and 175 bars.

Each of the lower spaces l4, l6, 18, 20 is connected to a pipe 25 through a path containing a non-return valve allowing flow of gas only in the direction into the respective lower space. In the drawing only the nonreturn valve 25 between the chamber 20 and the pipe 25 is provided with a reference numeral. The pipe 25 is connected to a gas reservoir (not shown) through a valve (not shown).

Each of the lower working spaces l4, 16, 18 and 20 is connected to two chambers, but in order to make the explanation more simple only the two chambers 27 and 28 adjacent to the low temperature working space 14 will be described, referring particularly to FIG. 2. The first one of said chambers namely the chamber 27 contains working gas at a pressure corresponding to the maximum working cycle pressure reached in the space 14 due to a non-return valve 29 arranged between the space 14 and chamber 27 and allowing flow of gas only in the direction from the space 14 into the chamber 27. The second one of said two chambers 27 and 28, namely the chamber 28, is connected to the chamber 27 through a non-return valve 30 allowing flow of gas only in the direction from the chamber 27 into the chamber 28.

A flexible wall 31 carrying a valve stem 32 separates the chambers 27 and 28, and the valve stem 32 governs a passage between the chamber 28 and the chamber 14. A permanently open restricted passage 33 is provided in a wall separating the chamber 27 from the space 14. The chamber 28 is connected to the corresponding chambers adjacent to the other low temperature working spaces of the engine by a system of pipes 34 leading to a valve (not shown) which controls the gas flow back to the reservoir (not shown).

The illustrated means for equalizing the mean pressures of the working gas charges will operate as follows:

During normal operation of the engine under constant load the gas pressure will vary between equal levels in the four separate working gas charges contained respectively mainly in the working spaces 19 and 20, 13 and 14, 15 and 16, andl7 and 18. Therefore, the nonreturn valves 26, 29 and 30 will not be operative. Minimum gas pressure will prevail in the pipe 25 and equal maximum pressures will prevail in the chambers 27 and 28 (and in the corresponding chambers adjacent to the other lower working spaces of the engine and in the pipe 34. i

If there is a gas leakage past a piston causing a decrease of the gas pressure in the lower working space 14 the non-return valve 29 will remain closed and gas will pass through the passage 33 from the chamber 27 into the working space 14. The pressure in the chamber 27 will now become lower than the pressure in the chamber 28, causing a downward movement of the flexible wall 31 and an opening of the passage between the chamber 28 and working space 14. Gas will now flow into the working space 14 until the pressures in the chambers 27 and 28 are equal to each other.

Simultaneously the said gasleakage from one of the four working gas charges past a piston causes an increase of the amount of gas in another of the gas charges with a consequent increase in the mean pressure in the working cycle thereof. This causes the corresponding valves 29 and 30 in the circuit for this working cycle to open and gas will flow into the pipe 34. This will increase the pressure difference across the flexible wall 31 and assist the opening of the passage governed by the valve stem 32, between the chamber 28 and the working space 14. Thus gas enters the working space 14 to compensate for the decrease caused by the leakage.

What we claim is:

l. A multiple cylinder Stirling cycle engine with a low temperature working space in each cylinder, a first chamber for each cylinder containing working gas at a pressure corresponding to the maximum cycle pressure of said low temperature working space in its associated cylinder, a second chamber for each cylinder containing working gas at a pressure corresponding to the maximum pressure reached during a working cycle in any one of said working spaces for said cylinders, means provided for comparing the pressures in said two chambers, and means for passing gas from said second chamber into said working space if the pressure in the second chamber exceeds that in the first chamber.

2. An engine as defined in claim 1 including a first non-return valve coupling said first chamber to said working space to permit gas to flow from said working space into said first chamber, and a second non-return valve permitting gas to flow from said first chamber into said second chamber.

3. An engine as defined in claim 2 wherein said means for passing gas comprises a valve between said second chamber and said working space, and wherein said means comparing the pressures in said two chambers operate said valve.

4. An engine as defined in claim 3 wherein said means comparing pressures is a flexible wall between said chambers operable to open said valve between said second chamber and said working space when the pressure of said second chamber exceeds that of said first chamber.

5. A Stirling cycle engine as defined in claim 1 including a restricted passageway between said first chamber and said working space allowing a minor flow of gas to pass in either direction.

6. An engine as defined in claim 5 including a one way valve between each said cylinder and its first chamber to permit flow into the chamber when the pressure of the working space exceeds that of the first chamber. 

1. A multiple cylinder Stirling cycle engine with a low temperature working space in each cylinder, a first chamber for each cylinder containing working gas at a pressure corresponding to the maximum cycle pressure of said low temperature working space in its associated cylinder, a second chamber for each cylinder containing working gas at a pressure corresponding to the maximum pressure reached during a working cycle in any one of said working spaces for said cylinders, means provided for comparing the pressures in said two chambers, and means for passing gas from said second chamber into said working space if the pressure in the second chamber exceeds that in the first chamber.
 2. An engine as defined in claim 1 including a first non-return valve coupling said first chamber to said working space to permit gas to flow from said working space into said first chamber, and a second non-return valve permitting gas to flow from said first chamber into said second chamber.
 3. An engine as defined in claim 2 wherein said means for passing gas comprises a valve between said second chamber and said working space, and wherein said means comparing the pressures in said two chambers operate said valve.
 4. An engine as defined in claim 3 wherein said means comparing pressures is a flexible wall between said chambers operable to open said valve between said second chamber and said working space when the pressure of said second chamber exceeds that of said first chamber.
 5. A Stirling cycle engine as defined in claim 1 including a restricted passageway between said first chamber and said working space allowing a minor flow of gas to pass in either direction.
 6. An engine as defined in claim 5 including a one way valve between each said cylinder and its first chamber to permit flow into the chamber when the pressure of the working space exceeds that of the first chamber. 